That is straight piracy right there, only 1/3 of everyone playing the game has paid you, they stole approx $50,000,000 USD ($25 x 2 million) from your pockets. Registered Users are pirates, don't think otherwise, that is straight fact right there. You don't even need evidence. They're stealing shit.

You need always on DRM to solve this problem. Use always on DRM and you instantly make $50,000,000 cause all those people will pay you.